1. Field of the Invention
The present invention relates to a method for manufacturing a magnetic recording medium in which a recording layer is formed in a concavo-convex pattern.
2. Description of the Related Art
Conventionally, a magnetic recording medium such as a hard disc has been significantly increased in areal density because of improvement such as fining magnetic particles composing a recording layer, material change, and increased precision in the processing of magnetic heads. Further increase in the areal density is expected in the future.
However, problems such as processing limits of magnetic head, side fringes due to the spread of a magnetic field, and crosstalk have become revealed, so that increase in the areal density by a conventional improvement method has reached its limitation. Thus, the so-called patterned medium type of magnetic recording medium such as a discrete track medium and a discrete bit medium has been proposed as a candidate for a magnetic recording medium which can realize the further increase in the areal density (refer to, for example, Japanese Patent Laid-Open Publication No. Hei 9-97419). In such a magnetic recording medium, a recording layer is formed in a concavo-convex pattern.
When the surface of the medium includes the concavo-convex pattern, on the other hand, there are cases where recording and reproducing characteristics become worse because the flying height of a head slider is unstable. Accordingly, it is necessary to deposit a non-magnetic material over the recording layer in the concavo-convex pattern for the purpose of filling concave portions with the non-magnetic material. Then, the excess part of the non-magnetic material above the recording layer has to be removed to flatten its surface.
A method of dry etching is available as a method for processing the recording layer into the concavo-convex pattern. A deposit technology such as sputtering, which is used in the field of semiconductor manufacturing, is available as a method for depositing the non-magnetic material. Also, a processing technology such as CMP (chemical mechanical polishing), which is used in the field of semiconductor manufacturing, is available as a method for removing the excess part of the non-magnetic material above the recording layer to flatten the surface.
In the CMP method, however, it is difficult to precisely control the amount of processing (thickness) in the order of 1 to 2 nm. Thus, there are cases where after the non-magnetic material above the recording layer is removed, a part of the recording layer is removed together with the non-magnetic material, and hence difference in the height of the surface contrarily increases because of difference between the processing rates of both.
The CMP method is a wet process. Accordingly, there is a problem that combining the CMP method and a dry process such as a processing process of the recording layer makes it complicated to convey an object to be processed and the like, so that the efficiency of the whole manufacturing process becomes worse.
When the CMP method is used, there is also a problem that slurry reacts with the recording layer and the magnetic characteristic of the recording layer tends to be degraded. Furthermore, there is a problem that using the CMP method takes much time and cost for cleaning and the like, because the slurry has to be removed.